Stabilizing chlorinated rubbery polymers



2 2,983,707 STABILIZING CHLORINATED RUBBERY POLYMERS Francis P. Baldwin, Colonia, Robert M. Thomas, West- 'field, and Irving Kuntz, Roselle Park, N.J., assignors to 13550 Research and, Engineering Company, a corporation of Delaware No Drawing. Filed Oct. 22, 1957, Ser. No. 691,557

4- Claims. (Cl. 260-453) This invention relates to rubbery polymeric compositions containing partially chlorinated copolymers of isoolefins and multiolefins, particularly chlorinated butyl rubber, and to the stabilization of such compositions. It also relates to compositions containing partially chlorinated (hereinafter referred to as chlorinated) copolymers of isoolefins and multiolefins together with minor proportions of certain organic aromatic or heterocyclic stabilizers. This is a continuation-in-part of US. patent application Serial No. 618,796 filed October 29, 1956.

In accordance with the present invention, it has now been found that while vulcanizates of isoolefin-multiolefin copolymers such asbutyl rubber do not respond by these stabilizing compounds as to resistance to oxidative degradation and as to heat aging resistance, particularly of the zinc oxide and/ or primary or polyfunctional amine-cured vulcanizates or covulcanizates.

In practicing the present invention, the unvulcanized chlorinated isoolefin-multiolefin-containing copolymer, prior to curing, is blended at a temperature between about and 200 C. with about 0.05 to 20, advantageously about 0.1 to 10.0, preferably 0.5 to 5.0 weight percent of one or more of the organic aromatic or heterocyclic stabilizing compounds enumerated hereinafter. This may be accomplished in several manners. in the preferred embodiment of the invention, about to %s of the organic stabilizing compound required is blended with the unvulcanized chlorinated copolymer slurry when the copolymer is recovered (i.e., precipitated rand/or injected into a hot aqueous medium) but prior to the drying, milling and/ or extruding steps.

. It is a further discovery of the present invention that when stabilized, chlorinated isoolefin-multiolefin copolymers (particularly chlorinated butyl rubbers, stabilized in accordance with the invention) are cured by zinc oxide and/or primary or polyfunctional amines in the substantial absence of added elemental sulfur and sulfur-containing ultra-accelerators such as derivatives of thiuram or carbamic acids, but in the presence of minor proportions of resinous polymerized hydroxy aromatic (or heterocyclic) dialcohol compounds, particularly about 0.1 to 20, preferably about 0.5 to 10.0.weight percent of dirnethylol phenolic resins, stabilized vulcanizates are produced which surprisingly exhibit not only resistance to thermal deterioration but also a combination of unusually high resistance to flexure and fatigue.

The foregoing dialcohol resins are produced by heating the monomeric phenol dialcohol at temperatures of between about 75 and 175 C. (e.g., 125 C.), care being taken to terminate the reaction while the resin is in the soluble (i.e., in organic solvents) and fusible state. Vulcanizates or covulcanizates of this last-mentioned type are especially useful in tires (especially in the carcass, undertread and bead areas), in tire casing curing bags or diaphragms, and in steam hose or similar articles.

The organic stabilizing compounds employed in accordance with the present invention have boiling points between about 100" and700 C. and are chosen from the category enumerated hereinafter, the members of which may be used singly or in combination.

tes Patent 2,983,707 Patented May 9, 1961 (I) Aromatic or heterocyolic amines such as substituted or unsubstituted poly-secondary amines having about 1 to 5 nitrogen atoms and containing attached to at least one nitrogen and/or carbon atoms, at least one (preferably 1 to 8) substituent having about 1 to 24, preferably about 1 to 18 carbon atoms; the substituents and total number of carbon atoms present in such compound being as set forth: said substituents being selected from the group consisting of alkyl, alkaryl, aryl, aralkyl, alkoxy, aryloxy, aroyl, acyl, acyloxy, and mixtures thereof. The total number of carbon atoms present in such compounds is generally, between about 7' and 60, advantageously about 7 to 48, and preferably about 8 to 42. Typical compounds falling within category (I) include: N,N-diphenyl-p-phenylene diamine; N,N'dioctyl-p-phenylene diamine; diphenyl ethylene diamine; p,p'-diamino diphenyl methane; and/or N,N'-di-beta-naphthyl-p-phenylene diamine.

copolymers of the general type hereinbefore mentioned, which are desirably chlorinated and stabilized with aromatic or heterocyclic compounds in accordance with the invention, especially Where the copolymer comprises a major proportion (preferably about to 99.5%) of a C to C isoolefin such as isobutylene, 2-methylbutene-l or 3-methyl butene-l, etc., with a minor proportion (preferably about 15 to 0.5 weight percent) of a multiolefin of about 4 to 14, preferably about 4 to 6 carbon atoms, are commonly referred to in patents and technical literature as butyl rubber, or GR-I rubber (Government Rubber-Isobutylene), for example in textbook Synthetic Rubber by G. S. Whitby. The preparation of butyl rubber is also described in US. Patent 2,356,128 to Thomas et al. and in US. application Serial No. 512,182, filed May 31, 1955, to Baldwin et al. The multiolefinic component of the copolymer is preferably a conjugated diolefin such as isoprene, butadiene, dimethylbutadiene, piperylene, or such multiolefins as cyclopentadiene, cyclohexadienes, dimetnallyl, allo-ocymene, vinyl fulvenes, etc. The copolymer comprising isobutylene and isoprene is preferred, although the copolymer may contain about 0.05 to 20.0, preferably about 0.2 to 5.0, parts by weight based on total reacting comonomers of such monoolefinic compounds as styrene, pmethyl styrene, alpha methyl styrene, indene, dihydronaphthalene, dichlorostyrene, p-chlorosty-rene, mixtures thereof, etc.

The chlorinated, rubbery isoolefin-multiolefin-containing copolymers, particularly chlorinated butyl rubbers, which are advantageously stabilized by aromatic or heterocyclic compounds in accordance with the present invention are derived from the foregoing isoolefin-multiolefin hydrocarbon copolymers. They are produced by carefully chlorinating these copolymers in a manner which does not degrade the molecular weight thereof, as more fully described hereinafter. The resulting chlorinated copolymers do not require sulfur or ultraaccelerators in their vulcanization and may be vulcanized solely by zinc Oxide and/or primary or polyfunctional amines. The vulcanizates and covulcanizates with other rubbery polymers such as natural and GR-S rubbers formed have been found to exhibit good stress-strain properties and to have superior heat aging resistance compared to the corresponding unchlorinated copolymers. Since these chlorinated copolymers already possess heat aging resistance superior to the unchlorinated copolymers, and the unchlorinated copolymers are not improved as to heat aging resistance by the addition thereto of aromatic and heterocyclic compounds hereinafter more fully described, it is most unexpected that such aromatic or heterocyclic compounds have now been found to even further improve aoearo'r containing copolymers are disclosed and claimed in copending application, Serial No. 512,182. In accordance with the disclosure of this last-mentioned application, butyl rubber or similar more highly unsaturated copolyrubber. This chlorinated rubber may then be separated from this slurry by filtration and drying or recovered as a crumb or as a dense sheet or slab by conventional hot milling and/or extruding procedures.

Isoprene (15)--.-

Isoprene (2) N ,N dlchloro 5,5- dlmethyl hydautoln.

mers or tripolymers are chlorinated so as to contain 5 As so produced, the chlorinated rubbery polymer has a about at least 0.5 weight percent (preferably at least Staudinger molecular Weight within the range between about 1.0 weight percent) combined chlorine but not more approximately 15,000 to 200,000, preferably about 25,000 than about X weight percent combined chlorine to 100,000; a Wijs iodine number between about 0.5 to wherein: 50, preferably about 5 to 15; and a mole percent unsatu- X 35461 X106 ration between about 0.1 to 30, preferably about 01.2 to 20.0. This copolymer, when cured, has a good e astic (100 L)M1+L(M2+35'46) limit, tensile strength, abrasion resistance and flexure and resistance and may be employed as an inner lining, the Percent of the multlolefin in the P ply, tread base, tread or sidewall in tires; in tire curing M r=m01eclllar Weight of the lsoolefin, bags or bladders, in rubber belting, in steam hose, as elec- M =molecular weight of the multiolefin, m insulation, em Weight of Chlorine- The uncured, chlorinated butyl rubber may be blended Suitable chlorinating agents which may be employed with about 0.5 to 10%, of a group II metal silicate, parare gaseous chlorine, alkali metal hypochlorites, C to ticularly calcium silicate, and/or with about 1 to 5% C tertiary alkyl hypochlorites, sulfur chlorides, pyriof an adsorbent deactivator such as various high boiling dinium chloride perchloride, N-chlorosuccinimide, alphtlpolar compounds, e.g., ethylene glycol, during or prefchloroacetoacetanilide, N,N'-dichloro-5,5 dimethylhyerably before the rubber is compounded with the hydantoin, trichlorophenol chloride, N-chloroacetamide, drated silica and curatives. beta-chloro-methyl phthalimide, etc. The preferred The amount of hydrated silica added, per 100 parts Chlorinafing agents are gaseous Chlorine, 'y chlO- by weight of chlorinated butyl rubber is generally about ride, chloro-hydantoins, and related materials. 10 to 75, preferably about 20 to 40 parts by weight for The chlorination is generally conducted at temperathe tie ply compositions, and somewhat higher, say about tures above about 0 to about +100 C., depending upon 20100, preferably about -75 parts for compositions the Particular Chlorinatillg agent, for 8about One minute t0 suitable for inner linings of tires. To the compound conseveral hours. An advantageous pressure range is from 30 taining about 0 to 100 parts by weight of hydrated silica, about 0.1 to 1000 p.s.i.a., atmospheric pressure being may al be bl nd d ab t 20 to 200 rts f a, carbon satisfacwl'y- The cbloifinafion y accomplished y black, preferably a thermal black for inner lining compreparing 1 to 50 or 80 weight perc nt S luti ns f 811611 positions or a channel-black (or thermal black) for tie copolymers as above, in a substantially inert liquid orply compositions. For inner lining compositions, about 0 garlic solvent such as a C to C substantially inert hydroto 200, preferably b t 50 t 150 parts b i ht f carbon of halogenated derivatives of Saturated y mineral filler may be desirably employed. Such fillers carbons; beXaIle, mineral P cyclbbbxal'le, include diatomaceous earth, montmorillonites, hard Zens. chlorobenzene, chloroform, carbon tetrachloride, clays, soft clays, talc, lithopone, barytes, or alumina, etc. ix s thereof, andedding theretothe chlorinating 4 vulcanization of such compositions as the foregoing, agent, which y Optionally be in Solution, Such as 0 when used in tie plies is generally for about 1 to 200 solved in a substantially inert hydrocarbon, an alkyl chlominutes at temperatures in the range of between about ride, carbon tetrachloride, carbon disulfide, etc. If chlo- 250 to 400 F, preferably about 270 to about 380 F. fine gas is p y it y also be diluted Wi p o In order to more fully illustrate the present invention, about 50 times its volume b preferably about 0.1 to115.0 th following experimental dat e given, times its volume of a su stantially inert gas suc as nitrogen, methane, carbon dioxide, etc. CHLORINATED RUBBERS A To K The resulting chlorinated isoolefin-multiolefin-contain- Eleven runs are made chlorinating isoolefin-multiolefin ing copolymer, particularly chlorinated butyl rubber copolymers. The amount of isoolefin and multiolefin in polymer, may be recovered by precipitation with oxycopolymer, chlorination agent, and amount of chlorine genated hydrocarbons, particularly alcohols or ketones combined in the copolymer are tabulated hereinafter. such as acetone or any other known non-solvent for the Bach recovery procedure is the same, namely by precipirubber and dried under about 1 to 760 millimeters or tation with acetone and redissolution in hexane three higher of mercury pressure absolute at about 0 to times. In each instance, when 100 parts by Weight of the 180 C., preferably about 50 to 150 C. (e.g. 70 C.). chlorinated copolymer formed is blended with 5 parts by Other methods of recovering the chlorinated polymer are weight of zinc oxide and 40 parts by weight of MP0 by conventional spray or drum drying techniques. Altercarbon black and then cured for 40 minutes at 300 F natively, the solution of the chlorinated rubber may be each resulting vulcanizate has a tensile'strength in excess injected into a vessel containing steam and/ or agitated of 1,000 psi. The molecular weight of each copolymer water heated to a temperature sufiicient to volatilize the is also not substantially degraded. The data is as solvent and form an aqueous slurry of the chlorinated follows:

Chlorinated Chlorination (Percent) Rubber Isoolefin (Percent) Multlolefin (Percent) Agent Cl in the Rubber Isobutylene (98).-. Isoprene S0201: 1.2 Isobutylene (97.5)- Isoprene (2.5)- C12 in 0014 1.4 Isobutylene Isoprene (5.0) C1: in 0014 2.5 Isobutylene (94)-.- Cyclopentadienc (6) C11 in C014 2.0 Isobutylene (92) Myrcene (8.0) Ch in 0014. 1.6 2-metl1yl-butene-1 (95). Isoprene (5).. C12 in CCh. 1.3 3-methy1-butcne-1 (96) Butadiene (4) C1: in C014. 1. 7 Isobutylene (9S l-vinyl cycloh Cl; m 0014 0.8 Isobutylene (92)..- Butadiene (8) C11 in G014 1.1

1 N ore-Percent in all instances is percent by weight.

Example I A master batch, in parts by weight, was prepared of the recipe; stabilized, chlorinated butyl rubber, 100 (8 minute Mooney viscosity at 212 F. of 71, mole percent unsaturation of 1.47 and containing 1.3 weight percent combined chlorine); SRF carbon black, 50; zinc oxide, 5; and stearic acid, 0.5. To a portion of this master batch were added one weight percent based on polymer of the stabilizer N,N'-di-beta naphthyl-p-phenylene diamine.

. After curing at 300 F. for 60 minutes, samples were placed in a circulating air oven maintained at a temperature level of 297 F. (147 C.) for various lengths of time and their volume swell in cyclohexane then determined. The results were as follows:

Example 11 A commercial butyl rubber polymer having a Mooney viscosity at 212 F. for 8 minutes of 46, a mole percent unsaturation by the drastic iodine-mercuric acetate method of 1.8 and a viscosity average molecular weight of 350,000, was chlorinated so as to contain 1.25% chlorine. The chlorinated copolymer formed was in admixture with 0.2 weight percent of the stabilizer 2,6-ditertiary butyl-4-methyl phenol. A sample of 100 parts by weight of this mixture was compounded in parts by weight into the formulation: SRF black, 50; zinc oxide, 5; stearic acid, 0.5; and the amounts indicated hereinafter of various stabilizers or combinations of stabilizers:

Example II 2,2 methylene bis (4 methyl 6 tertiary butyl phenol) 0.5 N,N'-di-beta-naphthyl-p-phenylene diamine 0.5

The resulting stabilized, chlorinated butyl rubbers were then cured for 60 minutes at a temperature level of 300 F., the following physical inspections being noted:

Property: Example '11 Tensile strength (p.s.i.) 1390 Elongation (percent) 410 Modulus at 300% elongation (p.s.i.) 1000 Samples of the respective cured vulcanizates were then placed in a circulating air oven maintained at 297 F. (147 C.) for various lengths of time and their volume swell in cyclohexane then determined. The results were as follows:

The above data show that chlorinated butyl rubber, stabilized in accordance with the present invention with an admixture of organic stabilizing compounds, exhibits good thermal aging properties. Also, the stabilized, chlorinated butyl rubber vulcanizates did not become appreciably soluble in the cyclohexane, were not embrittled and did not crack upon flexing. Unstabilized, chlorinated butyl rubber, although superior to unmodified butyl rubber or brominated butyl rubber, would heat age only for about /2 of the above periods of time of exposure. GRS or natural rubber when stabilized, compounded, treated and thermally aged as above, would become badly embrittled and would crack upon flexing. This example also illustrates theadvantage of the use of the amine compond of this invention in admixture with aromatic or heterocyclic compounds containing at least one hydroxyl radical and one other substituent such as allyl, alryl, alkoxy, etc.

The compositions comprising stabilized, chlorinated isoolefin-multiolefin copolymers, particularly stabilized, chlorinated butyl rubber, in accordance with the present invention, may be employed alone or in admixture with other rubbers for a wide variety of applications other than those mentioned hereinbefore such as in electrical insulation, inner tubes, blown sponge rubber, car window channel strips, proofed goods and other applications where unmodified butyl rubber or certain chloroalkadiene rubbery homopolymers or copolymers have utility.

Resort may be had to various modifications and variations of the foregoing disclosed specific embodiments and examples without departing from the spirit of the invention or the scope of the appended claims.

What is claimed is:

l. A composition consisting essentially of a major proportion of the reaction product at a temperature of above 0 C. to about 100 C. of a rubbery copolymer of about to 99.5 Weight percent of a C to C isomonoolefin and about 0.5 to 15 weight percent of a C to C diolefin with a chlorinating agent; said reaction product having a Staudinger molecular weight of about 15,000 to 200,000, a mole percent unsaturation of 0.2 to 20.0 and containing at least about 0.5 weight percent combined chlorine on a basis of the total weight of copolymer but not more than about 1 combined atom of chlorine per double bond in said copolymer and 0.5 to 20 weight percent of a stabilizer, said stabilizer being N,N'-di-beta-naphthyl-p-phenylenediamine.

2. A composition consisting of a rubbery copolymer having a Staudinger molecular weight of between 30,000 and 150,000, a mole percent unsaturation of 0.2 to 20.0 and containing atoms of hydrogen, carbon and chlorine and further containing in its structure about 85 to 99.5 weight percent of hydrocarbon units derived by the copolymerization of anisomonoolefin containing about 4 to 10 carbon atoms with about 0.5 to 15 weight percent of a diolefin containing about 4 to 14 carbon atoms; said copolymer containing at least about 0.5 weight percent chlorine combined therein at a temperature level of above about 0 C. to about C. but not more than about X weight percent combined chlorine wherein:

35.46L (100L)M1+L(M2+35.46) X 100 wherein:

L=mole percent of the diolefin in the copolymer M =molecular weight of the isomonoolefin M =molecular weight of the diolefin 35.46=atomic weight of chlorine;

said copolymer being in composition with about 0.1 to 20 weight percent of a stabilizer, said stabilizer being N,N-di-beta-naphthyl-p-phenylene diamine.

3. A composition according to claim 2 in which the stabilizer is a combination of N,N-di beta-naphthylp phenylene diamine and 2,2'-methylene-bis(4-methyl-6- tertiary butyl phenol) and 2,6-ditertiary buty1-4-methyl phenol.

7 4. An improved process for vulcanizing a butyl rubber copolymer of 85 to 99.5 weight percent of a C to C isomonoole'fin with 0.5 to 15% of a C to C diolefin which consists essentially of dissolving the unvulcanized copolymer in a solvent, chlorinating the copolymer at a temperature level of above 0 C. to about 100 C. to contain at least about 0.5 weight percent combined chlorine but not more than about 1 atom of combined chlorine per double bond in the copolymer, the chlorinated copolymer formed having a Staudinger molecular Weight of between about 15,000 and 200,000 and a mole percent unsaturation of 0.2 to 20.0, adding thereto about 0.1 to 20 weight percent of a stabilizer, said stabilizer being N,N-di-beta-naphthyl-p-phenylene diarnine and curing the resulting mixture at a temperature level of between about 250 and 400 F. in the presence of about 2 to 30 parts by Weight of a basic metal compound selected from the group consisting of group 11 metal oxides, group 11 metal carboxylates and mixtures thereof and about 0 to 20 parts by weight of an amino compound selected from the group consisting of primary amines, diarnines, and mixtures thereof, for about 1 to 200 minutes.

References Cited in the file of this patent UNITED STATES PATENTS 2,462,123 Nelson Feb. 22, 1947 2,529,060 Trillich Nov. 7, 1950 2,596,878 Van Vessen May 13, 1952 2,625,523 Garber et al. Jan. 13, 1953 2,716,096 Young et a1 Apr. 23, 1955 2,725,373 Reynolds Nov. 29, 1955 2,732,354 Morrissey et a1 Jan. 24, 1956 2,771,777 Allison et al Nov. 27, 1956 2,804,448 Hallenbeck Aug. 27, 1957 2,809,372 Fredrick et a1. Oct. 8, 1957 2,870,106 Ridgway et al. Jan. 20, 1959 2,877,189 Olin Mar. 10, 1959 2,891,595 Kuntz June 23, 1959 FOREIGN PATENTS 147,952 Australia Aug. 27, 1952 

1. A COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF THE REACTION PRODUCT AT A TEMPERATURE OF ABOVE 0* C. TO ABOUT 100* C. OF A RUBBERY COPOLYMER OF ABOUT 85 TO 99.5 WEIGHT PERCENT OF A C4 TO C10 ISOMONOOLEFIN AND ABOUT 0.5 TO 15 WEIGHT PERCENT OF A C4 TO C14 DIOLEFIN WITH A CHLORINATING AGENT, SAID REACTION PRODUCT HAVING A STAUDINGER MOLECULAR WEIGHT OF ABOUT 15,000 TO 2000,000, A MOLE PERCENT UNSATURATION OF 0.2 TO 20.0 AND CONTAINING AT LEAST ABOUT 0.5 WEIGHT PERCENT COMBINED CHLORINE ON A BASIS OF THE TOTAL WEIGHT OF COPOLYMER BUT NOT MORE THAN ABOUT 1 COMBINED ATOM OF CHLORINE PER DOUBLE BOND IN SAID COPOLYMER AND 0.5 TO 20 WEIGHT PERCENT OF A STABILIZER, SAID STABILIZER BEING N,N''-DI-BETA-NAPHTHYL-P-PHENYLENEDIAMINE. 